This application relates to magnetic disc drives and more particularly to an improved disc drive spindle motor apparatus for mounting information storage disc within the disc drive.
Disc drives are data storage devices that store digital data in magnetic form on a storage medium on a rotating information storage disc. Modern disc drives include one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g., a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Spindle motor assemblies often utilize a rotating spindle hub journaled to a non-rotatable spindle shaft. A disc clamp is typically secured to the rotating spindle hub to exert a downward axial force on the mounted information storage discs and disc spacers. Typically, the disc clamp exerts the downward force through a series of radially positioned screws torqued into the spindle hub. The radial positioning of the screws is beneficial for exerting clamping force on the spindle assembly because the force is exerted at the periphery of the clamp in closer proximity to the mounted information storage discs and disc spacers. However, the peripheral positioning of the series of screws in the disc clamp causes the downward force to be exerted in a non-uniform manner. Non-uniform clamping force can generally cause variations in the load force and, as a result, cause the top mounted information storage disc to be physically distorted. Distortion of the top disc, even by as little as 100 micro inches, can lead to operational errors during recording and reproduction of data on the information storage disc.
In a second type of spindle motor assembly the spindle shaft and spindle hub portion both rotate about a bearing sleeve. Here, a single screw can be used to secure the disc clamp to the rotating spindle shaft because the shaft rotates with the screw (as opposed to the non-rotatable shaft where a plurality of screws must be positioned about the shaft). However, in order to develop a clamping force with a single screw similar to the force developed by the plurality of screws surrounding the non-rotatable shaft, it is necessary to apply a much higher torque to the single screw. This relative high torque can lead to a number of problems including over-stressing the spindle shaft bearing and the generation of particles during the torquing process. These high-torque related problems can damage the bearing and lead to failure of the spindle motor. Currently, there is a need in the relevant art to overcome the shortcomings of the traditional single screw disc drive spindle motor assembly as well as the non-rotatable multiple screw spindle shaft spindle motor.
Against this backdrop the present invention has been developed. The present invention is an apparatus and method for uniformly loading information storage discs onto a spindle motor.
In accordance with a preferred method of the present invention, an information storage disc is assembled on a hub of a disc drive spindle motor and a disc clamp is positioned on the hub so that an outer periphery of the disc clamp engages a top surface of the assembled information storage disc. A predetermined pre-load force is applied to the disc clamp. A disc clamp nut is positioned on the pre-loaded disc clamp to secure the disc clamp to the hub and, once secured, the pre-load force is released from the disc clamp.
The present invention can further be implemented as a disc drive spindle motor assembly including a spindle having a shaft and a cylindrical hub extending radially outward from the shaft, the shaft including a threaded stud extending above a top surface of the cylindrical hub. One or more information storage discs are mounted on the cylindrical hub. A disc clamp having a central aperture, an inner annular contact portion, a middle annular raised portion and a peripheral edge is fitted over the threaded stud to allow the inner annular contact portion to engage the top surface of the hub while the peripheral edge engages the top surface of the information storage disc. The middle annular raised portion extends above the top surface of the hub and is adapted to receive a pre-load force. A disc clamp nut having a contact surface for engaging the inner annular contact portion of the disc clamp is fastened to the threaded stud and secures the pre-loaded disc clamp to the hub.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.